Synchronization methods for bus systems and the corresponding reception units are known. They are used, among other things, in fieldbus systems, e.g. the PROFIBUS, or other bus systems, such as the Ethernet. Fieldbus systems are distributed control systems which usually have a transmission unit (head assembly, bus master) and a multiplicity of reception units (slaves). The individual slave assemblies are usually driven by virtue of the transmission unit transmitting an instruction message to the reception units. Upon receipt of the instruction message, the reception units output to a controlled technical installation nominal values which have been transmitted to them previously by the transmission unit. At the same time, they read in from the controlled technical installation actual values which they subsequently transmit to the transmission unit. The transmission unit then calculates new nominal values which it transmits to the individual reception units, so that the reception units are ready for the next instruction message.
The instruction messages are sent by the transmission unit with equidistant timing. From the instruction messages it is therefore possible to derive synchronization signals which can be used to synchronize the reception units to the transmission unit. For producing relatively large networked systems on the basis of such bus systems or fieldbus systems, it is frequently necessary to synchronize a plurality of separate bus systems. In this context, it is also desirable to combine and hence also to synchronize different bus systems with one another.
In this case, great significance is attached to hierarchical structuring of bus systems, e.g. within the context of a local drive concept, where it is generally necessary for a controller, a plurality of drives and power sections to communicate with one another. Particularly in the field of numerically controlled industrial processing machines, e.g. machine tools and robots, having a plurality of interpolating axes, universal clock synchronization is demanded and may be required to access different bus systems. The latter instance is particularly desirable for increasing the flexibility and scope for use. Thus, there exists a need for an efficient method and system for synchronizing a plurality of bus systems.